When one encounters an opportunity to perform a mitzvah, he should immediately seize and complete it with haste out of fear lest impediments arise, and moreover, acting with external speed in performing a mitzvah generates and intensifies inner spiritual passion, whereas sluggish physical movement causes the spirit to diminish.
אֶלָּא בְּהַגִּיעַ זְמַנָּהּ אוֹ בְּהִזְדַּמְּנָה לְפָנָיו אוֹ בַּעֲלוֹתָהּ בְּמַחְשַׁבְתּוֹ, יְמַהֵר יָחִישׁ מַעֲשֵׂהוּ לֶאֱחֹז בָּהּ וְלַעֲשׂוֹת אוֹתָהּ וְלֹא יַנִּיחַ זְמַן לִזְמַן שֶׁיִּתְרַבֶּה בֵּינְתַיִם. כִּי אֵין סַכָּנָה כְּסַכָּנָתוֹ, אֲשֶׁר הִנֵּה כָּל רֶגַע שֶׁמִּתְחַדֵּשׁ, יוּכַל לְהִתְחַדֵּשׁ אֵיזֶה עִכּוּב לַמַּעֲשֶׂה הַטּוֹב. אַךְ הַזְּרִיזוּת אַחַר הַתְחָלַת הַמַּעֲשֶׂה הוּא, שֶׁכֵּיוָן שֶׁאָחַז בְּמִצְוָה, יְמַהֵר לְהַשְׁלִים אוֹתָהּ וְלֹא לְהָקֵל מֵעָלָיו כְּמִי שֶׁמִּתְאַוֶּה לְהַשְׁלִיךְ מֵעָלָיו מַשָּׂאוֹ, אֶלָּא מִיִּרְאָתוֹ פֶּן לֹא יִזְכֶּה לִגְמֹר אוֹתָהּ. וְאָמְנָם, הִתְבּוֹנֵן עוֹד, שֶׁכְּמוֹ שֶׁהַזְּרִיזוּת הוּא תּוֹלֶדֶת הַהִתְלַהֲטוּת הַפְּנִימִי, כֵּן מִן הַזְּרִיזוּת יִוָּלֵד הַהִתְלַהֲטוּת. וְהַיְנוּ, כִּי מִי שֶׁמַּרְגִּישׁ עַצְמוֹ בְּמַעֲשֵׂה הַמִּצְוָה כְּמוֹ שֶׁהוּא מְמַהֵר תְּנוּעָתוֹ הַחִיצוֹנָה, כֵּן הִנֵּה הוּא גּוֹרֵם שֶׁתִּבְעַר בּוֹ תְּנוּעָתוֹ הַפְּנִימִית כְּמוֹ כֵן, וְהַחֵשֶׁק וְהַחֵפֶץ יִתְגַּבֵּר בּוֹ וְיֵלֵךְ. אַךְ אִם יִתְנַהֵג בִּכְבֵדוּת בִּתְנוּעַת אֵיבָרָיו, גַּם תְּנוּעַת רוּחוֹ תִּשְׁקַע וְתִכְבֶּה. וְזֶה דָּבָר שֶׁהַנִּסָּיוֹן יְעִידֵהוּ.
Rather when the time of its performance comes, or when it happens to present itself to him, or when the thought of performing it enters his mind, he should hurry and hasten to seize hold of it and perform it, and not allow time to go by in between. For there is no danger like its danger. Since, behold each new second that arises can bring with it a new impediment to the good deed. The division of Zeal "after beginning a deed" is as follows. Since one took hold of a mitzva he should hasten to complete it. This is not in order to lighten on himself like one who desires to cast a burden off himself but rather out of fear lest he not merit to complete it. Reflect further that just like an inner fieriness of soul leads one to act with Zeal, so too the opposite, outwardly acting with Zeal leads to an inner fieriness of the soul. Namely, when one feels himself performing a Mitzva with great swiftness this will move his inner being to kindle aflame also, and the desire and want will increasingly intensify within him. But if he acts in a sluggish manner in the movement of his limbs, so too the movement of his spirit will die down and extinguish. This is something experience can testify to.